Non-return valve



FIG. 1 is a top, perspective view of the non-return valve;

FIG. 2 is a side elevational view of the non-return valve shown in FIG. 1;

FIG. 3 is a top plan view of the non-return valve shown in FIG. 1;

FIG. 4 is a side elevational view of the non-return valve shown in FIG. 1;

FIG. 5 is a cross-sectional view of the non-return valve shown in FIG. 1; and,

FIG. 6 is a bottom plan view of the non-return valve shown in FIG. 1.

Any portions shown in dashed or broken lines are included for illustrative purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a non-return valve, as shown and described. 